If so, would every bank need to halt trading in a currency before adding it?
Here's a more appropriate analogy. A penny stock with the symbol BCH is lightly traded over the counter by institutional investors via pink sheets. The New York Stock Exchange decides to list the stock for trading, making it easily available to everyone with a TD-Ameritrade/Robinhood/ETrade account but does so with no pre-announcement. Should NYSE prevent their employees from buying the pink sheet over the counter prior to the announcement?
The answer is Yes.
Banks will ban it's employees from buying those pesos because of something called "conflict of interest". It wouldn't matter if the price jumps or not. In fact, a conflict of interest can exist even if there are no improper acts as a result of it.
There are no laws against it for cryptocurrencies, yet. But, if something like this happened, it is unfair to Coinbase's customer.
For instance, employees of the SEC, are not prohibited from trading on insider information (they are to an extent, as in they can't do leveraged short-selling before in investigation is made public, however, for instance, selling out of a position before investigations become public knowledge is obviously common).
https://www.institutionalinvestor.com/article/b15dlrvg8cxkmv...
This is like asking "do high-level (and even medium-level) government employees have to pay taxes ?" (I'm European).
Shoutout to the rich guys that spread the misconception that an information advantage is illegal